A sequence consists of four squares already. The
fifth one is missing. It can be chosen from a number of options. The
task is to pick up the right one. For this you have to unveil the
sequence's prime clue.

Knowing the number of kisses and handshakes guests exchanged with each
other and with the hosts it is possible to answer how many of them arrived
at a dinner and if they arrived in couples or alone. Any ideas?